Ultrasonic Characterization of Polymers in Their Evolution From Solid to Liquid State

A polymer can be defined as a large molecule made of a number of repeating units. Actually many natural organic substances, such as hevea rubber, cellulose, starch, leather, proteins... are polymers. The hypothesis, that these materials are made of very long chains and that they owe their specific properties to this peculiar structure, was first put forth by Kekule in 1877. Since then, the macromolecular theory has been substantiated by its numerous success, both scientific — one of the most exhilarating being the discovery of the double helix structure for the DNA molecule by Crick, Watson and Wilkins (1953) — and industrial, with the advent of totally synthetic polymers which today represent an important portion of industrial materials.